Synthetic detergent formulations containing n-acyl taurates



United States Patent O SYNTHETIC DETERGENT FORMULATIONS CONTAINING N-ACYL TAURATES Henry Y. Lew, San Francisco, Calif., assignor to Cali- No Drawing. Application December 16, 1954 Serial No. 475,814

i- Claims. (Cl. 252-152) This invention relates to anionic synthetic detergent compositions capable of producing good-quality, stable and persistent foam upon being dissolved in water in concentrations conventionally employed in household washing and in commercial laundry practice.

Aqueous wash solutions of many known anionic synthetic detergents, when employed in non-automatic and automatic agitator-type washing machines, although efficient insofar as their detersive or cleansing action is concerned, are unsatisfactory with respect to their foam performance: (1) they produce very little foam in the presence of soil, (2) their foam usually has a lacy texture, and (3) during the agitation of the contents of. the tub of a washing machine the foam readily collapses and disappears.

g It is generally extremely difficult, if not impossible, to predict the foam characteristics of an anionic synthetic detergent containing, in addition to a sulfate or a sulfonate group, an intermediate linkage, e. g., an ester, an ether, or an amide linkage. Furthermore, one is never certain that a compound capable of improving the foam performance of a particular group of anionic organic sulfate or sulfonate detergents will similarly influence the foam performance of a different group of anionic sulfate or sulfonate detergents containing an additional or a different intermediate linkage. Thus, formulation of synthetic anionic detergent compositions possessing a high degree of washing efficiency and simultaneously capable of foam performance equivalent to that of the better household laundry soaps constitutes a dificult problem.

Water-soluble N-acylaminoalkanesulfonates of the formula:

wherein R may be a long alkyl chain containing from 9 to 17 carbon atoms, R may be hydrogen or a methyl radical, x may be an integer from 2 to 4, and M may be an alkali metal or ammonium cation have been known in the art as effective anionic detergents, stable in aqueous acid and alkaline solutions, and their preparation has been described. A conventional procedure involves reaction of an acyl chloride, such as oleoyl chloride or chloride of a fatty acid of the coconut oil group, with a taurine or an N-methyltaurine, followed by neutralization of the resulting N-acyltaurine, e. g., with NaOH, to obtain the desired N-acylaminoalkanesulfonate. These N- acylaminoalkanesulfonates can be also designated as N- acyltaurates.

Because of the abundance of tallow on the market, large quantities of inexpensive C -C saturated fatty acids are available for the manufacture of detergent N- acyltaurates. However, hydrolysis and hydrogenation of tallow, or like materials, yield mixtures of saturated fatty acids, in which palmitic (C and stearic (C acids predominate and in which the stearic acid content may be as high as 60-70% by weight. When watersoluble N acyltaurates are prepared by using individual saturated C andC fatty acids (palmitic and-stearie) 2,874,125 "Patented Feb. 17, 1959 ice and, particularly, by using mixtures of the saturated fatty acids recoverable by hydrolysis and hydrogenation from tallow, and are then employed as active components in detergent formulations, it is observed that dilute aque-- ous wash solutions of such formulations fail to produce a sufiiciently stable foam of a good quality. Furthermore, the volume of the foam produced is relatively low.. As a consequence, when used in washing machines atv conventional low concentrations (0.1 to' 0.4%), under conditions of agitation and in the presence of soiled clothes, these N-acyltaurates, fail to produce persistent suds in the tube of the machine, and the greyish, lacy suds soon disappear before the completion of the wash ing cycle (20 minutes or more). This inability to produce good-quality, stable and, consequently, per-- sistent suds explains the lack of demand for these N-- acyltaurate detergent compositions on the part of thefoam-conscious consumer who uses suds as an indicator or measure of the amount of detergent required for satisfactory washing.

I have found that synthetic detergent compositions con taining as their active organic detergent component a water-soluble N-acyltaurate of the aforedescribed type, when dissolved in water in concentrations from 0.1 to 0.4% such as are commonlyemployed in laundry practice, may be rendered capable of producing an adequate volume of stable, good-quality foam, persistant under the conditions of agitation in the presence of'soil, 'by incorporating into these compositions an effective proportion of certain monohydric and dihydric saturated straight-chain alcohols.

The alcohols operative in accordance with the invention include saturated straight-chain C -C and preferably C -C monohydric alcohols, such as n-dodecanol, n-tetradecanol, n-hexadecanol and also saturated straight-chain O -C 3 terminal vicinal dihydric alcohols, e. g., tetradecane-1,2-diol, hexadecane-LZ-diol, octadecane-l,2-diol. The amounts of these normal monohydric and dihydric alcohols effective in improving the foam performance of synthetic detergent compositions containing water-soluble N-acyl taurates, may range from about 1% to about 5% by weight based on the total weight of the detergent composition. These alcohol additives are not affected by the presence of hypochlorite bleaches in the wash solutions of detergent compositions containing them. The term terminal vicinal dihydric alcohols as employed in this specification and in the claims means those glycols (or diols) having the two hydroxyl groups attached to adjacent carbon atoms at the end of the hydrocarbon chain.

A portion of the active N-acyltaurates derived from hydrogenated tallow fatty acids may be replaced by the well-known C C monoalkylbenzenesulfonates, in proportions as high as 95%, but preferably not exceeding 85% by weight of the total active organic component of the detergent composition. This replacement tends to enhance the volume of foam that can be produced by the dilute aqueous wash solutions of these detergent compositions, without any noticeable interference with the improvement in the static (mechanical) stability and persistence of the foam, due to the introduction of monohydric and 1,2-dihydric C -C aliphatic alcohols in the manner described hereinbefore.

While the quantity of detergent C -C monoalkylbenzenesulfonates, which may be present in the compositions of the invention replacing a portion of N-acylless than 50% by weight may also be used in replacing a portion of the N-acyltaurate in the active organic detergent component. The quantity of the monohydric or dihydric normal saturated C C aliphatic alcohol effective in providing the desired degree of foam persistence and stability under agitation in the presence of soil, in any instance, should range from 1% t and preferably from 2% to 3% by weight-of the total solids in the detergent composition.

The use of monoalkylbenzenesulfonates as a substitute for a portion of N-acyltaurates tends to reduce significantly the overall costs of formulating the detergent compositions, without adverse effects on the beneficial action of monohydric and dihydric alcohol additives on the foam performance of N-acyltaurates. The preparation of these detergent sulfonates is known in the art and is described, e. g., in U. S. Patent No. 2,477,383 to Lewis and U. S. Patent No. 2,218,472 to Kyrides.

The excellent foam properties of the detergent compositions of the invention are not affected adversely by the presence therein of inorganic salt builders commonly employed in anionic detergents, and particularly in the so-called heavy-duty detergents. These builders are neutral salts of strong inorganic acids (chlorides or sulfates), and alkaline salts of weak inorganic acids (carbonates, phosphates, borates, etc.). I have found that the improved detergent compositions of this invention, in addition to N-acyltaurates as the active component (either with or without admixture of monoalkylbenzenesulfonates) and in addition to the monohydric or dihydric normal saturated C -C aliphatic alcohol as the foam-improving agent, may contain in each 100 parts by weight based on the total content of solids in the detergent formulation, from 60 to 90 parts by weight of the aforesaid water-soluble inorganic builders, sodium salt being usually preferred. These sodium salts include sodium carbonate, sodium tripolyphosphate, tetrasodium pyrophosphate, sodium chloride, borax, etc.

Well-known fatty acid alkylolamide foam improvers such as lauric isopropanolamide and lauric ethanolamide may be present, if so desired, in conventional small quantities in the detergent compositions of the invention, improving thereby the tolerance of soil by the foam, likewise without interfering in any manner with the beneficial effect of monohydric and dihydric alcohol additives on foam persistence under the conditions of agitation in contact with soil.

Furthermore, other conventionally employed additives such as anti-caking agents, optical bleaches, silicates as corrosion inhibitors, perfumes and dyes may be present in conventional amounts in the detergent compositions. Carboxymethyl cellulose or celluronic acid salts may also be introduced to prevent redeposition of the soil, and N-alkyl glycines and diglycines may likewise be added to prevent occurrence of skin rashes and erythemeas. All of the aforesaid additives are employed in small amounts less than 5% by weight, based on the total content of solids in the composition, and in all events in such amounts as not to interfere with the improvement in foam performance in accordance with the invention.

Generally, the various ingredients of my detergent compositions are blended by dissolving them in water to form a solution or slurry, and subsequently drying the homogenized blend to a solid particle form; or evaporating it to form a paste; or diluting it to give a liquid concentrate.

Foam evaluation bench tests were carried out at the laboratory using aqueous wash solutions of the detel-gent composition prepared in accordance with the invention. Also, a number of tests employing the same solutions was conducted in an agitator-type non-automatic washing machine under conditions closely approaching those of the conventional operation of a household. washing machine.

In a representative test series, each 100 parts by weight of the solid detergent formulation contained from 2O termediate stabilities are rated as fair.

to 22 parts by weight of a combination of the following organic ingredients: active N-acyltauratc, active monoalkylbenzenesulfonate and a saturated monohydric or dihydric straight-chain C -C aliphatic alcohol in the proportions within the ranges hereinbefore specified. Sodium C C polypropylene benzene sulfonate was employed as a representative monoalkylbenzenesulfonatc. The taurate component was N-acyl (tallow acid) N- methyl taurate derived from hydrogenated tallow fatty acids (runs Nos. 1 to 7) and N-palmitoyl N-methyl taurate (runs Nos. 8 to 18). In the test runs Nos. 19, 20 and 21 the taurate was N-oleoyl N-methyltaurate, a surfactant differing in foam behavior from the tallow acid-derived N-acyltaurates and tauratcs of C and C saturated fatty acids. A number of representative monohydric and dihydric saturated aliphatic alcohols from the group of alcohols operative in accordance with my invention were employed as foam-stabilizing agents.

Inorganic detergent builders and additives were present in the following amounts: 30 parts by weight of sodium tripolyphosphate; 20 parts by weight of tetrasodium pyrophosphate; 5 parts by weight of liquid sodium silicate; the remainder to make parts by weight sodium sulfate. Sodium silicate had a Na O:SiO ratio of 1:32. The detergent product was dissolved in soft water from the laboratory tap (50 p. p. m. of Ca-Mg hardness) at F. to make up 500 ml. of a 0.15% solution in a 2 liter beaker. Water hardness is represented in parts per million of calcium acid magnesium calculated as CaCO and MgCO in a weight ratio of 2:1. The solutions were then tested at the bench by agitating the contents of the beaker with the aid of a propeller-type stirrer for one minute. The contents were then allowed to stand for one minute, and foam heights in mm. were determined. In another 15 minutes after the termination of the agitation, the foam heights were measured again. Stability of the foam was rated by observing the rate of foam decay under mechanical stress,

as by blowing on a small volume of foam gently with air. When the foam withstands being blown upon, its stability is good. An unstable foam rapidly collapses when blown upon; its stability is rated to be poor. In-

Foam of good quality is made up of uniformly small-sized, densebodied bubbles of high bulk viscosity. It is white and opaque. Foam of a poor quality has large-sized bubbles, a low bulk viscosity and tends to be lacy. It is, furthermore, greyish in color and more transparent. The foam intermediate in quality between poor and good foam is rated to be fair.

In testing foam persistence under the conditions of agitation in a washing machine, the tub or bowl of the machine was filled with soft water (50 p. p. m.) containing a 0.15 concentration of the detergent formulation to a standardized level and then was charged with a load of soiled cotton towels. The 50 p. p. In. figure for water hardness represented parts per million of calcium and magnesium calculated as CaCO and MgCO in a weight ratio of 2:1. The contents of the tub were agitated in each test under identical conditions and at the same temperature (120425 F.) The rating of foam persistence was carried out as follows: When the suds disappeared from the surface of the wash solution in less than 5 minutes after the beginning of agitation, the persistence was given a rating of 1. When the foam took from 5 to 10 minutes to disappear, the persistence was rated as 2. When from 10 to 20 minutes was required for the foam to disappear, the persistence was given a rating of 3. The foam which lasted for 20 minutes, but was less than /2 inch high above the surface of the liquid in the tub was given a rating of 4. Whenever after 20 minutes of operation the foam height was from /2 to 1% inches above the surface of the liquid, the persistence was assigned a rating of 5. When after 20 minutes the foam retained a height of 1% to 3 inches above the surface of the liquid, thepersistence-was ratedas 6. Finally, when the foam after 20 minutes possessed a higher level than 3 inches above the surface of the liquid, the per- 6 detergent component a mixture of an N-acyltaurate, such as N-tallow acid"-N-methyltaurate or N-palmitoyl-N- methyltaurate, with detergent monoalkylbenzenesulfonate, such as C to C polypropylenebenzenesulfonate,

sistence was assigned a maximum rating of 7. 5 in combination with a saturated monohydric or dihydric The data from several representative test runs 1llus- C12-C1g allphatic alcohol, particularly wlth the C alcotratmg the advantages of the improved detergent comhol, aqueous solutions of such compositions produced a positions of the present invention are tabulated 1n the suflicient volume of stable, good-quality foam to assure following table: the desired degree of perslstence (ratings 5 and 6). The

TABLE I Foam evaluation data Mono- Bench test Washalkyling mabenchine Test Sodium N-acyl N-methyl- Parts Foam-stabilizing Parts zene- Foam height test, in run taurate acyl group derived by agent by sul- Foam Foam soft No. fromweight weight fonate, stabilqualwater parts After After ity ity (50 by 1min. 15min. p,p.m.) weight 1 A mixture of hydrogenated 20 0 38 29 tallow fatty acids. 2 do 10 0 10 62 2s 10 2 10 s0 s2 2 1 19 a3 a 3 2 17 so 65 2 10 as 78 3 2 17 85 68 10 2 10 84 7o 5 2 83 67 a 2 15 84 72 2 2 1c 83 a5 1 1 18 79 e7 2 2 16 st 70 s 2 1s 88 7a 0 0 60 as 1 18 2 0 32 29 Good" Fair... 3 0 2 20 78 12 Poor do.. 4 1s 2 0 4s 38 Fair... "no... 10 2 10 e0 50 .do .do 5 2O 0 0 (i8 43 Poor" Poor 4 10 0 10 77 58 do .do 0 0 20 89 72 .d0... do-. 1

Detergent compositions containing an N-acyl-(tallow acid)-taurates as the only active ingredient, in the absence of straight-chain saturated C to C alcohols as foam-stabilizing agents, furnished a very low volume of foam of a poor quality which lacked mechanical stability (run #1). Consequently, foam persistence in the washing machine test was totally inadequate (rating 1). The same observations were made in the case of compositions in which the active N-acyltaurate component was derived from an individual saturated C fatty acid of the hydrogenated tallow fatty acid group, namely, from palmitic acid. When N-palmitoyltaurate was the only active organic detergent ingredient, and in the absence of the foam-stabilizing alcohol additive (e. g., run 15), the foam lacked the necessary mechanical (static) stability and was of a poor quality. Addition of a saturated C to C straight-chain alcohol, without replacing a portion of the taurate by a monoalkylbenzenesulfonate detergent, improved the mechanical stability and the quality of the foam; however, the foam volume was low, and adequate foam persistence in the washing machine test could not be attained (run 16). As could be expected, compositions based on alkyl benzene sulfonate as the only active organic ingredient produced a large volume of a Weak, lacy foam, relatively poor in mechanical stability and, consequently, in persistence under conditions of agitation (run 22). Introduction of an alcohol additive failed to remedy the poor foam performance of such sulfonatebased composition (run 17) When a portion of the N-acyltaurate active component in the detergent composition was substituted by the detergent monoalkylbenzenesulfonate, the foam volume increased; however, the static stability and quality of the foam were poor, and, as a consequence, the foam persistence under agitation was inadequate (run 2).

On the other hand, when the detergent compositions have been formulated by using as their active organic effectiveness of such compositions is illustrated in the table by runs 3-14, inclusive.

In contrast with the foam behavior of N-acyltaurates derived from saturated fatty acids of hydrogenated tallow, N-acyltaurates of unsaturated fatty acids, such as oleic acid, disclosed in the prior art respond but slightly to the additions of alkylbenzenesulfonates (run 21); of aliphatic C -C alcohols effective in compositions Where the saturated acyl group of the N-acyltaurate contains from 13 to 17 carbon atoms (run 18); or of both (run 19).

The washing efficiency of aqueous solutions of deter gent compositions of the present invention, based on the organic active detergent component consisting of N-acyltaurates of hydrogenated tallow fatty acids alone or in a mixture with detergent monoalkylbenzenesulfonates, and containing an effective proportion of a saturated C C aliphatic monohydric or dihydric alcohol as the foam-stabilizing agent, compares favorably with that of conventional laundry soap.

It is to be understood that the foregoing description and the examples in the table do not limit the invention, and have been offered solely to illustrate the operativeness of the detergent compositions hereinafter claimed.

I claim:

1. A detergent composition consisting essentially of a water-soluble N-acylaminoalkane sulfonate detergent having 2 to 4 carbon atoms in the alkane portion of the molecule and being derived from C -C hydrogenated tallow fatty acids, a water-soluble C C monoalkyl benzene sulfonate detergent, the former being present in an amount of about 25% to 50%, by weight, and the latter 75% to 50%, by weight, of the total of the two, and as a foam-improving agent from about 1% to 5%,

by weight, based on the total solids content of said detergent composition, of a (E -C saturated straight chain alcohol selected from the group consisting of monohydric alcohols and 1,2-glycols.

2. A built detergent composition consisting essentially of 10 to 40%, by weight, of the detergent composition of claim 1 and 90 to 60%, by weight, of water-soluble inorganic salt builders.

3. A detergent composition according to claim 1, wherein the foam-improving agent, is present in an amount of 2 to 3%.

4. Composition according to claim 1, wherein the foam-improving agent is a C -C13 monohydric alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 2,166,315 Martin July 18, 1939 2,315,983 Ross Apr. 6, 1943 2,477,383 Lewis July 26, 1949 2,679,482 Ross May 25, 1954 2,746,932 Vitale May 22, 1956 2,758,092 Peck Aug. 7, 1956 OTHER REFERENCES Ross and Miles: Oil and Soap (American Oil Chemists Society Journal), May 1941, pages 99-102. 

1. A DETERGENT COMPOSITION CONSISTING ESSENTIALLY OF A WATER-SOLUBLE N-ACULAMINOALKANE SULFONATE DETERGENT HAVING 2 TO 4 CARBON ATOMS IN THE ALKANE PORTION OF THE MOLECULE AND BEING DERIVED FROM C16-C18 HYDROGENATED TALLOW FATTY ACIDS, A WATER-SOLUBLE C16-C18 MONALKYL BENZENE SULFONATE DETERGENT, THE FORMER BEING PRESENT IN AN AMOUNT OF ABOUT 25% TO 50%, WEIGHT, AND THE LATTER 75% TO 50%, BY WEIGHT, OF THE TOTAL OF THE TWO, AND AS A FOAM-IMPROVING AGENT FROM ABOUT 1% TO 5%, BY WEIGHT, BASED ON THE TOTAL SOLIDS CONTENT OF SAID DETERGENT COMPOSITION, OF A C12-C18 SATURATED STRAIGHT CHAIN ALCHOL SELECTED FROM THE GROUP CONSISTING OF MONOHYDRIC ALCHOLS AND 1,2-GLYCOLS.
 2. A BUILT DETERGENT COMPOSITION CONSISTING ESSENTIALLY OF 10 TO 40%, BY WEIGHT, OF THE DETERGENT COMPSOITION OF CLAIM 1 AND 90 TO 60%, BY WEIGHT, OF WATER-SOLUBLE INORGANIC SALT BUILDERS. 